The neural bases of decisions involving risky or delayed monetary rewards have been studied extensively with neuroimaging in humans. However, little is known about what mediates individual variability in decisions, and even less is known about individuals'differential responses to social rewards. In contrast to monetary rewards, the hedonic value of social rewards is immediately consumed at presentation. Social rewards additionally have a rich evolutionary history: humans have evolved to process and make decisions about social stimuli. Nevertheless, very little is known about how humans process and make decisions about social rewards. My proposed research therefore seeks to characterize the neurobiological underpinnings of social reward processing and decisions involving social rewards using functional magnetic resonance imaging (fMRI). Subjects will passively receive social rewards and will also make decisions involving social rewards. In the first experiment, subjects will make decisions involving delayed social rewards. In the second experiment, subjects will make decisions involving probabilistic social rewards. The core hypothesis for the first two experiments is that subjects'neurometric representation of value for social rewards (i.e., social reward sensitivity) within ventromedial prefrontal cortex (vmPFC) will predict individual differences in risk preferences and discounting rates for social rewards. The final experiment of the project seeks to examine the underlying functional differences in the reward circuitry that mediate individual differences in social reward sensitivity by using functional connectivity analyses. The prediction for the final experiment is that increased functional connectivity between ventral striatum and vmPFC predicts increased social reward sensitivity. Collectively, the proposed experiments will further our understanding of decision making processes by extending current models of decision making to include social rewards. The distinction between normal and dysfunctional decision making has significant implications for mental health since many psychopathologies involve dysfunctions in decision making. The neural mechanisms that mediate normal decision making and individual differences in behavior are not well understood. An enhanced understanding of the biology underlying inter-individual variability in decision making may lead to a better understanding of the etiology of several diseases and disorders of mental health;therefore, the proposed project seeks to characterize the neural underpinnings that lead to these individual differences.